For a practitioner of communication science and technology, seeking a novel method to increase channel capacity of a system without increased bandwidth is a subject for ever. At present, there are established technologies for improving channel capacities of conventional wireless communication systems. People are resorting to non-conventional electromagnetic wave field for technical breakthroughs. According to classical electrodynamics theories, vortex electromagnetic waves of same frequency and different modes may share channels at the same time. Bo Thidé and his Italy colleague team have demonstrated the experiment of independent information transmission at the same time in the same frequency with vortex wave and planar wave, which verified the capability of improving channel capacity of a wireless system with vortex wave, providing a new way for further increasing channel capacity of existing communication systems.
In order to apply vortex wave technology to the radio frequency band, continuous efforts have been made. Main research achievements reported in publications in the art are as follows. In 2010, S. M. Mohammadi and Bo Thidé et al. proposed a method for generating vortex waves based on a ring array antenna. In 2011, F. Tamburini et al. experimentally verified a method for generating vortex waves with an aperture antenna having an 8 order spin ladder-shaped reflector. In 2012, Alan Tennant et al. verified by simulation the method for generating vortex waves o independent modes at a plurality of frequencies at th same time using a TSA (Time Switched Array) ring array. In 2013, Qiang Bai and Tennant A et al. simulated a method for generating vortex waves with an 8 element phased microstrip uniform circular array. In 2014, Qiang Bai et al. verified experimentally the generation of vortex waves with 8-element phased microstrip uniform circular array antenna. In 2014, Palacin B et al. studied the application of 8×8 Butler matrix in th 8-element uniform circular array antenna and generated 8 vortex waves of independent modes at the same carrier frequency at the same time. In 2015, Wei Wen-long et al. designed a ring phase shifter with a carrier frequency of 2.5 GHz for a 4-element phased microstrip uniform circular array vortex EM antenna. In 2015, Gui Liang-qi et al. from Huazhong University of Science and Technology simulated the method for generating vortex waves with grooved circular array antenna.
As reported in prior art publications, the larger the number of available modes for the vortex waves in a communication system is, the more significant the capacity improvement for the system is, and accordingly the larger the physical dimensions required for the system receiving/transmitting antennas, which is adverse to the movement and maintenance of the communication system. Therefore, studying technologies for generating high order vortex waves with antennas of relatively small physical dimensions has theoretical and practical significance. at present, there are rare reports about the method for generating and receiving high order multi-mode vortex waves in wireless communication field.